709 research outputs found
Influence of κ-carbide interface structure on the formability of lightweight steels
κ-carbide (κ) in high aluminium (Al) steels is grown from austenite (γ) via γ → γ + κ or γ → α + κ (α represents ferrite), and is a lamellar structure. This work demonstrates that the formability of high Al lightweight steels is affected by the lattice misfit and interface shape between κ and matrix. The cold workability can be improved by either to change the steel chemical constitution or to implement an electro-thermo-mechanical process. For ferrite-matrix-based high Al steel, electric-current promotes the spheroidization and refinement of κ structure and reduces volume fraction of κ phase. This retards the crack nucleation and propagation, and hence improves the materials formability. The observation is caused by a direct effect of electric-current rather than side effects
Seismic Analysis of Prestressed Bridge Pier Based on Fiber Section
AbstractFiber model analysis method based on flexibility method is carried out to build analysis model for integral cast in-situ prestressed bridge piers, and the nonlinear time-history analysis is conducted with the low-peried cyclic loading. The hysteretic behavior of prestressed reinforced concrete pier and common reinforced concrete pier are compared and analyzed. The results showed that prestressed reinforced concrete pier has preferable re-centring capacity, smaller residual deformation and worse energy dissipation capacity. Along with the increase of distance from prestress location to section centroid, the tension degree of prestressed reinforcements and the reinforcement ratio come a decrease the residual deformation and energy dissipation capacity of pier
Stability of martensite with pulsed electric current in dual-phase steels
Softening frequently occurs in dual-phase steels under isothermal tempering of martensite. Recently, non-isothermal tempering is implemented to decrease the softening process in dual-phase steels. Here, we have discovered using high power electropulsing treatment can significantly enhance the strengthening effects via the formation of ultrafine-grained ferrite with nano-cementite particles in tempered martensitic-ferritic steels. To the best our knowledge, electropulsing treatment is a proper candidate to retard even to recovery the softening problems in the tempering of martensite in comparison with other isothermal and non-isothermal tempering methods
Experimental Investigation on the Tensile Strength of Composite Laminates Containing Open and Filled Holes
An experimental study is performed to evaluate
the effects of clamping pressure, friction, and
washer size on the static performance of composite
laminates with open and bolt-filled holes.
The static tensile strength and failure behavior
of composite laminates with an open hole and a
bolt-filled hole are analyzed and compared. Experimental
results show that the static tensile
strength of composite laminates is sensitive to
pre-existing damage of both open- or filled-hole
laminates. In contrast, a comparison between
the experimental results of open- and filled-hole
specimens proved that whether the hole is open
or filled has a feeble influence on the tensile-tensile
fatigue strength of studied composite laminates.
In comparison, however, it is found that
the inserted washer size, bolt clamping force,
and friction force strongly affect the tensile
strength of open- and filled-hole composite laminates.
Moreover, application of thicker washers
and hi-lock bolt will significantly increase
the static strength and fatigue life of composite
laminates with a bolt-filled hole.Экспериментально оценено влияние силы зажима, трения и размера шайбы на статические
характеристики слоистых композитов со сквозными и болтовыми отверстиями. Проведено
сравнение статического предела прочности при растяжении и характера разрушения слоистых композитов со сквозным и болтовым отверстиями. Результаты экспериментальных
исследований показали, что на статический предел прочности при растяжении слоистых
композитов влияет изначальное повреждение независимо от наличия сквозного или болтового
отверстия. Сравнительный анализ результатов исследований образцов со сквозным и болтовым отверстиями подтвердил тот факт, что вид отверстия (сквозное или болтовое)
незначительно влияет на усталостную прочность при растяжении исследуемых слоистых
композитов. Установлено, что такие факторы, как размер шайбы, сила зажима болта и
сила трения, существенно влияют на предел прочности при растяжении слоистых композитов со сквозным или болтовым отверстием. Использование утолщенных шайб между
слоистым материалом и болтом-заклепкой значительно увеличивает статическую прочность и долговечность слоистых композитов с болтовыми отверстиями.Експериментально досліджено вплив сили затиску, тертя і розміру шайби на статичні
характеристики шаруватих композитів із наскрізними і болтовими отворами. Проведено порівняння статичної границі міцності при розтязі і характера руйнування
шаруватих композитів із наскрізними і болтовими отворами. Результати експериментальних досліджень показали, що на статичну границю міцності при розтязі
шаруватих композитів впливає початкове пошкодження незалежно від наявності
наскрізного чи болтового отвору. Порівняльний аналіз результатів досліджень зразків із наскрізними і болтовими отворами підтвердив той факт, що вид отвору
(наскрізне чи болтове) незначно впливає на міцність від утомленості при розтязі
досліджуваних шаруватих композитів. Установлено, що такі чинники, як розмір
шайби, сила затиску болта і сила тертя, суттєво впливають на границю міцності при
розтязі шаруватих композитів із наскрізним чи болтовим отвором. Використання
стовщених шайб між шаруватим матеріалом і болтом-заклепкою значно збільшує
статичну міцність і довговічність шаруватих композитів із болтовими отворам
Removal of MnS inclusions in molten steel using electropulsing
A method using electropulsing to separate inclusions from molten steel is developed, based on the differences in electrical properties between the inclusions and liquid metal. The inclusions have different electrical resistivity from that of the liquid steel and hence are expelled to the surface of the metal by electropulsing. In comparison with the as-solidified untreated steel, the size of the inclusion is significantly larger at the surface of the molten steel due to the enhanced agglomeration. Moreover, the technique is efficient in eliminating particles smaller than 20 μm
Functional diversity of chemokines and chemokine receptors in response to viral infection of the central nervous system.
Encounters with neurotropic viruses result in varied outcomes ranging from encephalitis, paralytic poliomyelitis or other serious consequences to relatively benign infection. One of the principal factors that control the outcome of infection is the localized tissue response and subsequent immune response directed against the invading toxic agent. It is the role of the immune system to contain and control the spread of virus infection in the central nervous system (CNS), and paradoxically, this response may also be pathologic. Chemokines are potent proinflammatory molecules whose expression within virally infected tissues is often associated with protection and/or pathology which correlates with migration and accumulation of immune cells. Indeed, studies with a neurotropic murine coronavirus, mouse hepatitis virus (MHV), have provided important insight into the functional roles of chemokines and chemokine receptors in participating in various aspects of host defense as well as disease development within the CNS. This chapter will highlight recent discoveries that have provided insight into the diverse biologic roles of chemokines and their receptors in coordinating immune responses following viral infection of the CNS
Observation of exclusive DVCS in polarized electron beam asymmetry measurements
We report the first results of the beam spin asymmetry measured in the
reaction e + p -> e + p + gamma at a beam energy of 4.25 GeV. A large asymmetry
with a sin(phi) modulation is observed, as predicted for the interference term
of Deeply Virtual Compton Scattering and the Bethe-Heitler process. The
amplitude of this modulation is alpha = 0.202 +/- 0.028. In leading-order and
leading-twist pQCD, the alpha is directly proportional to the imaginary part of
the DVCS amplitude.Comment: 6 pages, 5 figure
Complete measurement of three-body photodisintegration of 3He for photon energies between 0.35 and 1.55 GeV
The three-body photodisintegration of 3He has been measured with the CLAS
detector at Jefferson Lab, using tagged photons of energies between 0.35 GeV
and 1.55 GeV. The large acceptance of the spectrometer allowed us for the first
time to cover a wide momentum and angular range for the two outgoing protons.
Three kinematic regions dominated by either two- or three-body contributions
have been distinguished and analyzed. The measured cross sections have been
compared with results of a theoretical model, which, in certain kinematic
ranges, have been found to be in reasonable agreement with the data.Comment: 22 pages, 25 eps figures, 2 tables, submitted to PRC. Modifications:
removed 2 figures, improvements on others, a few minor modifications to the
tex
A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments
We measured the inclusive electron-proton cross section in the nucleon
resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2
with the CLAS detector. The large acceptance of CLAS allowed for the first time
the measurement of the cross section in a large, contiguous two-dimensional
range of Q**2 and x, making it possible to perform an integration of the data
at fixed Q**2 over the whole significant x-interval. From these data we
extracted the structure function F2 and, by including other world data, we
studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate
higher twist contributions. The small statistical and systematic uncertainties
of the CLAS data allow a precise extraction of the higher twists and demand
significant improvements in theoretical predictions for a meaningful comparison
with new experimental results.Comment: revtex4 18 pp., 12 figure
eta-prime photoproduction on the proton for photon energies from 1.527 to 2.227 GeV
Differential cross sections for the reaction gamma p -> eta-prime p have been
measured with the CLAS spectrometer and a tagged photon beam with energies from
1.527 to 2.227 GeV. The results reported here possess much greater accuracy
than previous measurements. Analyses of these data indicate for the first time
the coupling of the etaprime N channel to both the S_11(1535) and P_11(1710)
resonances, known to couple strongly to the eta N channel in photoproduction on
the proton, and the importance of j=3/2 resonances in the process.Comment: 6 pages, 3 figure
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